2003 Seattle Annual Meeting (November 25, 2003)
Paper No. 183-10
Presentation Time: 4:00 PM-4:15 PM


MOLINARI, Mark P. and BURK, Robert L., URS Corporation, 1501 4th Avenue, Suite 1400, Seattle, WA 98101-1616, mark_molinari@urscorp.com

An E-NE trending reverse fault is inferred to underlie the coastal plain between Mukilteo and Everett, Washington. Evidence for the fault is a 300m wide, asymmetric anticline in strata mapped as Late Pleistocene age Whidbey Fm. (Minard 1982, 1985) exposed in a series of deeply incised creek channels. The fold limbs consist of well bedded, fine-medium sandstone that dips 75N and 47S. Vertical to overturned dips in sandstone and recumbent and overturned folds within stratigraphically lower mudstone occur in the fold core. The contact between the Whidbey Fm. and the overlying non-glacial sand and gravel and glaciolacustrine clay and silt (transitional beds of Minard) is an angular unconformity. However, these younger strata are also deformed with dips ranging from 6 to 20. Housing obscures the coastal plain surface, but there are discontinuous, post-glacial linear breaks in slope that may be of tectonic origin. The structural trend and overall fold shape suggest a N-dipping reverse fault, similar to the Seattle fault, is located near the southern margin of the Everett basin. This structure is conjugate to the nearby, NW-trending, right-lateral South Whidbey fault. Assessment of the recency and lateral extent of deformation is ongoing and will be presented.

2003 Seattle Annual Meeting (November 25, 2003)
Session No. 183
New Views of Seismic Hazard in Cascadia I: Seismology and Seismotectonics II
Washington State Convention and Trade Center: Ballroom 6C
1:30 PM-5:30 PM, Tuesday, November 4, 2003

Geological Society of America Abstracts with Programs, Vol. 35, No. 6, September 2003, p. 479

© Copyright 2003 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.